U.S. patent number 3,580,530 [Application Number 04/802,192] was granted by the patent office on 1971-05-25 for lift fan installation of vertical or short take-off and landing aircraft.
This patent grant is currently assigned to Japan Aircraft Manufacturing Co., Ltd.. Invention is credited to Kiyoshi Soda, Misao Wada.
United States Patent |
3,580,530 |
Wada , et al. |
May 25, 1971 |
LIFT FAN INSTALLATION OF VERTICAL OR SHORT TAKE-OFF AND LANDING
AIRCRAFT
Abstract
A lift fan installation of vertical or short takeoff and landing
aircraft has a single or plurality of lift fan assemblies, and a
casing or casings for housing said lift fan assembly. Said lift fan
assembly involves a gas generator, a fan driven by the fluid
derived from said generator, and an engine body in which said
generator and fan are disposed. Between the inner wall of the
casing and the outer wall of the engine body is defined an air
passage, the effective cross-sectional area of which is less than
one and a half times that of the exhaust duct of said lift fan
assembly.
Inventors: |
Wada; Misao (Fujisawa-shi,
JA), Soda; Kiyoshi (Yokohama-shi, JA) |
Assignee: |
Japan Aircraft Manufacturing Co.,
Ltd. (Yokohama-shi, JA)
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Family
ID: |
13751413 |
Appl.
No.: |
04/802,192 |
Filed: |
February 25, 1969 |
Foreign Application Priority Data
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Nov 9, 1968 [JA] |
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43-81622/68 |
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Current U.S.
Class: |
244/54; 60/264;
244/12.3 |
Current CPC
Class: |
B64C
29/0016 (20130101) |
Current International
Class: |
B64C
29/00 (20060101); B64c 029/04 (); F02k
003/04 () |
Field of
Search: |
;60/226,262,264
;244/12,12 (A,B)/ ;244/52,53,54 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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788,290 |
|
Dec 1957 |
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GB |
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967,780 |
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Aug 1964 |
|
GB |
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1,009,269 |
|
Nov 1965 |
|
GB |
|
Primary Examiner: Hart; Douglas
Claims
We claim:
1. In a lift fan installation of vertical or short takeoff and
landing aircraft comprising at least one lift fan assembly and at
least one casing for housing said at least one lift fan assembly,
each lift fan assembly including a gas generator, a fan driven by
fluid derived from said generator, an exhaust duct and an engine
body in which said generator and fan are disposed, the improvement
comprising an air passage provided between the inner surface of
said casing and the outer surface of said engine body, and a
plurality of doors hinged on the upper periphery of said casing to
form an extension of the incoming flow path through said casing
when said doors are opened.
2. A lift fan installation as claimed in claim 1, further
comprising a plurality of exhaust doors hinged on the lower
periphery of said casing to form an extension of the exhaust flow
path through the casing when said exhaust doors are opened, said
exhaust doors being superposed on each other when closed.
3. A lift fan installation as claimed in claim 1, wherein the
effective cross-sectional area of said air passage is less than one
and one-half times that of said exhaust duct of said lift fan
assembly, and wherein said air passage continuously surrounds said
engine body.
Description
This invention is concerned with improvements in a lift fan
installation of vertical or short takeoff and landing aircraft so
as to increase the thrust per lift fan assembly.
It has been an important problem in the aircraft industry to
increase an effective thrust generated by a lift fan assembly
without increasing its weight and bulk. Developments heretofore
made have generally been directed to improvement in the efficiency
of the lift engine.
In contrast, the present invention consists in utilizing the dead
space between the inner wall of a casing and the outer wall of the
engine body of a lift fan assembly.
This was found during an attempt to utilize the principle
underlying the prior art by applying a more advanced theory related
thereto.
Said principle was detailed in Theodore Von Karman's report
entitled "Theoretical Remarks on Thrust Augmentation." His report
states that if a fluid flowing through a cylindrical tube provided
with a jet nozzle is considered to be incompressible, the thrust
augmentation of the fluid may be determined from the following
equations:
Au.sub.1 +aU=(A+a)u.sub.2 (1)
(A-a)(u.sub.1 .sup.2 /2)+aU.sup.2 =(A+a)u.sub.2 .sup.2 (2) where a
denotes the cross-sectional area of the jet nozzle, A the balance
of the cross-sectional area of the cylindrical tube from which has
been subtracted said area a, U the velocity of the fluid jetted
through the jet nozzle, u.sub.1 the velocity of the fluid flowing
between the walls of the cylindrical tube and jet nozzle, and
u.sub.2 the fluid velocity in the cylindrical tube downstream of
the outlet of the jet nozzle.
From the equations (1) and (2) above, may be derived the
following:
where .phi. represents the thrust augmentation ratio and .nu.
denotes a value represented by a fraction a over A. In this case,
if .nu. is larger than 1, .phi. will assume a value below
unity.
This appears to be theoretically unreasonable, and indicates the
impossibility of utilizing the dead space between the inner wall of
the casing and the outer wall of the engine body of the lift fan
assembly so as to improve the substantial efficiency of the lift
engine, because the cross-sectional area of said dead space is
defined as small as possible in general design, for example, said
area having a smaller value than that of the jet nozzle or one and
a half times the latter area.
These inventors have found that Karman's principle disregards the
reduction of static pressure at the outlet of the jet nozzle, with
the resultant augmentation of jet velocity.
They have corrected the equation (3) by including a new factor in
the augmentation of jet velocity as follows:
An object of this invention is to provide a lift fan installation
of vertical or short takeoff and landing aircraft so improved as to
be put to practical use due to the theoretical proof of the
equations corrected by these inventors.
In an aspect of this invention, a lift fan installation of vertical
or short takeoff and landing aircraft involves a single or
plurality of lift fan assemblies, and a casing or casings for
housing said lift fan assembly, said lift fan assembly having a gas
generator, a fan driven by the fluid derived from said generator,
and an engine body in which said gas generator and fan are
disposed, and is characterized by an air passage defined between
the inner wall of the casing and the outer wall of the engine body,
the effective cross-sectional area of said passage being less than
one and a half times that of the exhaust duct of said fan
assembly.
Said air passage can be made by utilizing the dead space without
increasing the weight and bulk of the lift fan installation.
The invention in now described in conjunction with preferred
embodiments with reference to the accompanying drawings, in
which:
FIG. 1 is a diagram of the thrust augmentations obtained from these
inventor's equations and Karman's equations;
FIG. 2 is a plan view of a lift fan installation embodying this
invention;
FIG. 3 is a vertical cross-sectional view of said lift fan
installation taken along a line III--III of FIG. 2;
FIG. 4 is a vertical cross-sectional side view of said lift fan
installation taken along a line IV-IV of FIG. 2;
FIG. 5 is a vertical cross-sectional view of a lift fan
installation modified from that of FIGS. 2 to 4;
FIG. 6 is a vertical side view of a lift fan installation, partly
broken, further embodying this invention;
FIG. 7 is a plan view of an airplane equipped with lift fan
installations of this invention;
FIG. 8 is a front view of said airplane of FIG. 7;
FIG. 9 is a side view of an airplane of FIG. 7;
FIG. 10 is a plan view of an airplane equipped with lift fan
installations at different positions from those of FIGS. 7 to
9;
FIG. 11 is a plan view of said installations disposed at a further
different position from those of the two above-mentioned
airplanes;
FIG. 12 is a plan view of said installations located at still
further different parts of an airplane; and
FIG. 13 is a side view of said airplane of FIG. 12.
A lift fan installation of vertical or short takeoff and landing
aircraft (hereinafter called "V/STOL aircraft") embodying this
invention has been made available for practical use by the
discovery that the dead space of the installation can be fully
utilized by applying the equations corrected by these inventors.
The thrust augmentation .phi. which has been made possible by the
varied area ratio A/a derived from the inventor's equations is
indicated by line A in FIG. 1, while that based on Karman's
equations is indicated by line B in the same figure. Said lift fan
installation of the V/STOL aircraft can be designed without
increasing its weight and bulk substantially within the range of
the area ratio A/a 1.5.
Said lift fan installation is constituted by a plurality of lift
fan assemblies such as turbojets 1 and a lift fan pod 2 with a
casing 3 for containing said lift fan assemblies. Said lift fan
assembly involves a gas generator, a turbofan driven by the
generator and a circular engine body 4 surrounding said generator
and fan. Between the inner wall of the casing 3 and the outer wall
of the engine body 4 is formed an air passage 5 which is the key
part of this invention. Bracket members (not shown) for causing the
lift fan assemblies 1 to be supported by the casing 3 are
fabricated preferably in such a manner that the air is passed
through the passage 5 without being deflected.
In the embodiment of FIG. 3, the lift fan pod 2 has a pair of
intake doors 6 disposed on both upper sides thereof, a pair of
exhaust doors 7 disposed on both lower sides thereof and front and
rear doors 8 positioned at the front and rear portions of the
exhaust of the air passage 5. These doors 6 to 8 are hinged on the
outer wall of the pod 1 in a manner to surround the air passage 5,
thereby to form additional air passages 9 and 10 communicating with
the air passage 5 when opened. Said additional passages 9 and 10
are effective to maintain the clear fluid stream so that the thrust
of the fluid through the casing and lift fan assembly is
effectively utilized. In order to form the passage 10 as long as
possible, said exhaust doors 7 are so arranged as to be superposed
on each other when closed. The operation of these doors is remote
controlled by suitable means, for example, hydraulic control means
(not shown). The aforesaid arrangement is detailed in the
embodiment of FIGS. 2 to 4.
Another embodiment of this invention is indicated in FIG. 5. The
lift fan installation of said embodiment specifically involves an
annular member 11 for causing the exhaust gas from the lift fan
assembly to be mixed with the air through the air passage.
A further embodiment of this invention is indicated in FIG. 6,
wherein each of the lift fan assemblies can be rotated in a
vertical plane extending from the front portion to the rear portion
of the installation.
According to this invention, the effective cross-sectional area of
the air passage 5 is set at a value less than one and a half times
that of the exhaust duct of the lift fan assembly thereby to
utilize the dead space between the inner wall of the casing 3 and
the outer wall of the engine body 4 which has been unavoidably left
unused in the conventional design of said lift fan
installation.
An airplane 12 indicated in FIGS. 7 to 9 is equipped with lift fan
installations of this invention which are positioned at the
intermediate portions 13 of the wings 14 thereof. Therefore, each
of said installations has two pods 2a and 2b jointly connected to
each other via a structure 15 provided for connecting the
installation with the wing. In each pod are disposed a plurality
of, for instance, three lift fan assemblies 1a, 1b and 1c.
An airplane 12a indicated in FIG. 10 is characterized by having the
lift fan installations of this invention positioned at the free
ends 13a of the wings 14a thereof.
An airplane 12b indicated in FIG. 11 is characterized by having the
lift fan installations of this invention, each of which comprises a
lift fan pod 2c and two lift fan assemblies 1d and 1e and which are
capable of being housed in the body of said airplane. Namely, each
of the lift fan pods is supported by a bar member 16 which is
rotatably secured to the body. Said lift fan pods are respectively
put in or out of housings 17 formed in the side portions of the
body by the operation of the bar member.
An airplane 12c indicated in FIGS. 12 and 13 is characterized by
having the lift fan installations of this invention, wherein
casings 3a are housed in wings 14b and respectively contain a lift
fan assembly.
Of course, the position of the lift fan installation may be
selected as required in design.
* * * * *